Putin has no realistic security concerns with NATO. "Europe" is a tiny thumb land mass dwarfed by Russia, and the Eastern European countries formerly dominated by Russian military are tiny pebbles in comparison. The countries in the EU have a long history of minimal funding for their militaries and given the history of the last century only an unsane person would fear an invasion of Russia from the West.

Putin does have a rational fear of liberal democracies with rule of law and human rights protections. He has already enriched himself to the point of being the wealthiest person on the planet and that kleptocratic reality is only threatened by the political sentiments of the Russian public. These could conceivably be swayed by political and economic realities on his borders.